Noise

Aircraft noise is a key concern for the Zurich Airport Group, in particular at its home base as Zurich Airport has by far the most flight movements and the greatest number of residents affected by noise.

The Zurich Airport Group is aware that aviation noise can be a nuisance and that there is a growing need for information and action. Transparent information and dialogue with residents are key. The company has reported on the measures it has taken and provided updates on noise statistics and flight operations for many years already. For instance, the number of take-offs and landings at Zurich, broken down by runways and flight paths, is reported on the company’s website each day. Zurich residents affected by aircraft noise can call or e-mail Flughafen Zürich AG directly with any queries or concerns and staff from the Noise Management department will respond to specific questions.

In the reporting period, residents complained most frequently about the perceived increase in traffic and inbound flights from the south in the evening hours. Nevertheless, the total number of enquiries and complaints declined slightly compared with the previous year (see Noise statistics).

In order to take stock of the noise situation and collect noise-related charges, it is necessary to have accurate measurements of noise levels. Data on air traffic noise in the vicinity of Zurich Airport have been collected since 1966. A network of noise monitoring stations at currently 14 fixed locations near departure and arrival routes is operated. The system automatically links the noise data recorded to the corresponding flight movements. These data are published monthly in a noise bulletin that can be freely accessed on the company’s website. As prescribed by the Sectoral Aviation Infrastructure Plan (SAIP), exposure to aircraft noise and the progress made with mitigation measures are analysed in a comprehensive report each year which is shared with FOCA. This report is then used as the basis for any corrective action, for example optimising processes for long-haul flights taking off in the evening, or incentivising airlines by increasing noise charges for departures after 11 p.m.

Following the sharp drop in take-offs and landings in 2020 due to the Covid-19 pandemic, the number of flight movements increased again during the year under review. As a result, all monitoring stations registered more aircraft noise both during the day and at night.

Take-off routes from Zurich Airport were configured to avoid low overflights of densely populated areas wherever possible. The Noise Management department monitors all departures from Zurich Airport for adherence to the prescribed flight paths. These are mandatory during daytime at least up to an altitude of 5000 feet (approximately 1500 metres above sea level) and at night up to flight level 80 (approximately 8000 feet or 2500 metres above sea level). Compliance with these noise-optimised flight paths is monitored with the aid of the Airport Track And Noise Monitoring System (ATANOMS). An aircraft may only deviate from the prescribed flight path if there is good reason to do so, for instance to avoid storm clouds or following instructions from an air traffic controller. If there is no legitimate reason, an investigation is triggered, and the pilot in question will be asked to submit a statement in writing. These investigations often also involve interviews with representatives of the airlines. If the investigators are not satisfied, the matter may be referred to the Federal Office of Civil Aviation (FOCA). This constant monitoring encourages the airlines to optimise the take-off phase at all times.

As in the previous year, instructions from air traffic control were the most frequent legitimate reason cited for flight path deviations. 89 (2020: 83) investigations into unjustified deviations were launched and 13 (2020: 18) interviews with chief pilots were conducted.

Residents in the region perceive night-time flights to be particularly intrusive. In particular, noise between 11 p.m. and 11.30 p.m. often gives rise to complaints. This period can be used to work off the backlog of delays built up over the day. Together with the airlines and ground handling agents, Flughafen Zürich AG has taken steps to reduce the number of flights during this period. Measures include optimising operational processes, increasing noise surcharges and prioritising the long-haul flights scheduled for 10:40 p.m. and 10:45 p.m. Analyses carried out prior to the pandemic indicate that the measures taken have helped improve the situation.

In 2021, night flights (between 10 p.m. and 6 a.m.) accounted for only 3.5% (2020: 3.0%) of flight movements. Special authorisations were issued for a total of 75 flights (2020: 69) during the night-time curfew period (11.30 p.m. to 6 a.m.). Such night flights are only authorised when there are legitimate grounds, for example for emergency landings or for rescue, police, disaster relief, government or calibration flights (see Noise statistics).

The soundproofed hangar built at Zurich Airport in 2014 greatly helps to reduce the noise from engine ground testing. The hangar allows engines from aircraft up to the size of a Boeing 747-800 to be tested. Although it greatly reduces noise exposure for nearby residents, the hangar does not eliminate noise completely, so limits apply to the number of tests that may be run.

A total of 377 (2020: 406) engine ground tests were carried out in the noise protection hangar during 2021. The majority of engine tests carried out at night were for short-haul and medium-haul aircraft (80% of all night-time engine tests). Most engine tests for long-haul aircraft such as the A343, A333 and B777 and all other aircraft types were performed during the day. The permitted noise level was exceeded in six individual time windows in 2021. This is significantly fewer than the 25 instances per year permitted by the operating regulations. According to figures provided by the aircraft maintenance companies, 865 idle tests were performed on the apron and on the stands. 314 of these were run at night (10 p.m. and 6 a.m.).

At the beginning of December in the reporting year the noise protection hangar was damaged during an engine test and had to be taken out of service. Until it is fully repaired, which is likely to take several months, engine ground tests will have to be run outside.

Levying noise-related charges gives airlines a financial incentive to operate the quietest possible aircraft on their Zurich routes. All jet aircraft are assigned to one of five noise categories, each of which has a different charge rate based on the time of take-off and landing. In addition, the rates for night-time flights vary according to noise category and the specific take-off or landing time.

A total of CHF 6.5 million in revenue was generated from aircraft noise charges in 2021. Of this, CHF 3.8 million were from standard charges applicable to all 24 hours, and CHF 2.7 million were from surcharges levied during shoulder periods and at night (9 p.m. to 7 a.m.). The surcharges were last adjusted in 2019.

As the airport’s operator, Flughafen Zürich AG is obliged to protect residents of properties in the vicinity of the airport who are exposed to excessive aircraft noise. Along with reducing engine noise, the company’s sound insulation programme is a key element of its aircraft noise mitigation efforts. Flughafen Zürich AG funds passive sound insulation measures, primarily the installation of sound-insulating windows, in buildings in the surrounding communities. Owners of properties with noise-sensitive rooms which are located within a clearly defined perimeter, and which were not subject to any obligation to install sound insulation during construction or conversion, are eligible to benefit from the programme. Property owners who have already taken the initiative of fitting sound-insulating windows themselves are reimbursed by Flughafen Zürich AG.

From 1999 through 2021, approximately CHF 289 million was spent on sound insulation measures in around 5350 buildings. In contrast to the 2020 Annual Report, the number of properties no longer includes ones that are not eligible. Of CHF 14.5 million expenditure in 2021, CHF 0.6 million was spent on project planning, CHF 10.2 million on window upgrades and CHF 3.7 million on reimbursements.

As air traffic noise can affect the value of a property, the company is faced with around 20,100 claims for compensation from property owners around Zurich Airport. The compensation claims were submitted at the time the airport was privatised and following the imposition by Germany of restrictions on flight approaches over its territory. Any new claims may now only be submitted if there are substantial changes to flight operations; as a result no further claims have been submitted to Flughafen Zürich AG since then. Of the compensation claims received, as at the end of 2021 over 14,496 (72%) had been concluded, with CHF 85.6 million being paid in noise compensation. All noise compensation claims are paid from the Airport Zurich Noise Fund (AZNF).

As there are very few provisions regarding noise compensation or direct overflights in federal legislation, every open question of law must first be tested in the relevant courts. Legal test cases are being conducted in the interests of processing outstanding claims efficiently. They are helpful both for clarifying open questions of law and for obtaining legal rulings regarding the specific situation in the various airport regions.